https://www.sciencedaily.com/releases/2021/09/210916173428.htm

"Our latest study provides further evidence of the importance of airborne transmission," said Dr. Don Milton, professor of environmental health at the University of Maryland School of Public Health (UMD SPH). "We know that the Delta variant circulating now is even more contagious than the Alpha variant. Our research indicates that the variants just keep getting better at travelling through the air, so we must provide better ventilation and wear tight-fitting masks, in addition to vaccination, to help stop spread of the virus."

The amount of virus in the air coming from Alpha variant infections was much more -- 18-times more -- than could be explained by the increased amounts of virus in nasal swabs and saliva. One of the lead authors, doctoral student Jianyu Lai explained that, "We already knew that virus in saliva and nasal swabs was increased in Alpha variant infections. Virus from the nose and mouth might be transmitted by sprays of large droplets up close to an infected person. But, our study shows that the virus in exhaled aerosols is increasing even more." These major increases in airborne virus from Alpha infections occurred before the Delta variant arrived and indicate that the virus is evolving to be better at travelling through the air.